CODEWITHSUNDEEP
c++data-structuresdictionaryhashmapmultimap
Rajeshwar
Rajeshwar

Reputation: 11651

Difference between multimap and unordered map

I was reading about c++ multimap and it states that multimap allows inserting duplicate Keys.This makes me think that a multimap uses a hashmap for underneath implementation (since a hashmap allows duplicates incase of collision) then I also read that unordered map uses a hash map. My question is then whats the difference between the two. I tried looking for comparison between the two but I could not find anything that would explain this.

Upvotes: 4

Views: 4640

Answers (1)

user395760
user395760

Reputation:

A hash table permits and resolves collisions of hash values. It only stores one copy of each key value (as determined by operator== or another equality relation). But if two distinct keys hash to the same value (bound to happen), that is handled by collision resolution. For each key, there is a single value.

A multimap is an ADT that associates multiple values with each key instead of one. It's not a particular implementation strategy: It can internally use a hash table, a search tree, or something completely different.

Upvotes: 4

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